In the centuries that have passed since the premiere of Johann Sebastian Bach’s St. Matthew Passion in Leipzig’s St. Thomas’s Church at the Good Friday service in 1727, the work has had a remarkable performance history. Despite the fact that it received a number of repeat performances during Bach’s own lifetime (in revised versions), the St. Matthew Passion was largely forgotten after the composer’s passing until Felix Mendelssohn “resurrected” it in Berlin in 1829 with the localSing-Akademie and the Philharmonische Gesellschaft. The latter performance created such a level of excitement and interest in musical circles that two repeat performances followed soon after, despite Mendelssohn’s absence from Berlin. In 1970, Nikolaus Harnoncourt’s groundbreaking Telefunken LP of the St. Matthew Passion with the period instrument band Concentus Musicus Wien was released, a recording that, above all, stood in stark contrast to the consistent growth in the size of choirs performing this work that had occurred over centuries since Bach’s first performance in 1727. As with Mendelssohn’s performance, Harnoncourt’s interpretation generated great interest in scholarly circles and among the listening public. This critical commentary examines the size and constitution of the vocal and instrumental forces of all three performances of the St. Matthew Passion, as well as the extent to which those of 1829 and 1970 adhered to what is known of Bach’s own practices. In addition to investigating the choices made by the respective musical directors in this respect, the reception of Mendelssohn’s and Harnoncourt’s performances will also be considered.